A charged particle beam apparatus includes: an optical system that irradiates a sample mounted on a sample stage with a charged particle beam; at least one detector that detects a signal generated from the sample; an imaging device that acquires an observation image; a mechanism for changing observation positions in the sample which has at least one of a stage that moves the sample stage and a deflector that changes the charged particle beam's irradiation position; a display unit that displays an operation screen provided with an observation image displaying portion that displays the observation image and an observation position displaying portion that displays an observation position of the observation image; and a controller that controls display processing of the operation screen. The controller superimposes and displays on the observation position displaying portion a plurality of observation position images at different magnifications, based on the observation images' magnifications and coordinates.